1. Field of the Invention
The present invention relates to a manufacturing equipment using ion beam or electron beam that processes samples by use of ion beams.
2. Background Art
In recent years, attention has been focused on inspection and analysis techniques for reducing the manufacturing costs of semiconductor devices represented by microprocessors, semiconductor memories represented by dynamic random-access memories, electronic parts such as magnetic heads and the like. Optimizing process conditions and making failure analyses and the like efficient by putting inspection and analysis techniques to full use to contribute to the shortening of development periods and early improvements in yield.
Examples of inspection and analysis apparatus include a dual beam FIB-SEM system in which a focused ion beam (hereinafter abbreviated as “FIB”) device and a scanning electron microscope (hereinafter abbreviated as “SEM”) are combined. An FIB-SEM system has the function of irradiating a sample with FIBs and forming a section in the sample by the sputtering action, and it is possible to observe the section of a defective portion under a SEM. However, a SEM having a resolution on the order of several nanometers has already been insufficient for observing the construction of leading-edge devices for which miniaturization is moving forward. Therefore, a technique has come to be used which involves cutting out a defect-including microsample having a side on the order of 10 μm from a sample by using FIBs and a probe without cutting off the sample, taking out the microsample to outside the apparatus, and observing the microsample under a scanning transmission electron microscope (hereinafter abbreviated as “STEM”) or a transmission electron microscope (hereinafter abbreviated as “TEM”), both having a subnanometer-level resolution.
In a general FIB device, a gallium (GA) ion source is used, and gallium remains around a processed hole after the picking-out of a microsample. It is very probable that the remaining gallium will cause a defect in the following semiconductor manufacturing process. Particularly, the remaining gallium becomes a P-type impurity for a silicon semiconductor. Therefore, if an FIB-treated wafer is returned to the line as it is, the gallium diffuses and there is a high possibility that this induces deterioration in mechanical properties. For this reason, it is impossible to return a wafer from which a microsample has been picked out by using FIBs again to the production line and hence such wafers has to be discarded. Because recently the diameter of wafers has become larger and the number of processes has been increasing, the damage by the discarding of such wafers has amounted to a great amount of money.
Against this background, there has been available a method that involves using, as ion species for sample processing, ions of inactive gases of argon, krypton, xenon, etc., nitrogen gas, oxygen gas and the like in place of gallium as a technique for preventing gallium pollution (refer to JP Patent No. 3564717, for example). In this method, a microwave plasma, which is a nonpolar discharge, is used in an ion generation source and extracted, an ion beam of a target ion species is extracted by use of an electrode and an accelerating electrode, and the section of a sample processed by the extracted ion beam is observed under a SEM.
However, in the above-described conventional technique, a nonmetallic gas ion beam is used as a processing ion beam and metal pollution sometimes occurs when a sample is processed mainly during a malfunction of an FIB-SEM system. For example, this is a case where a power supply control system is stopped to protect the power supply in association with a short-circuit discharge that frequently occurs immediately after the maintenance of an ion generation source.
For example, when the applied voltage of a condenser lens changes from a normal value to zero, with the processing beam extracted, the beam diameter becomes large compared to a normal operating condition, and portions not irradiated with the beam in a normal operating condition (the electrode, inner wall of the column and the like) are irradiated with the beam, with the result that if the irradiated portion is made of metal, a material sputtered with the ion beam reaches the sample, causing metal pollution. Similarly, when the applied voltage and acceleration voltage for extracting the processing beam change from normal values to zero, the beam divergence angle changes and portions not irradiated with the beam in a normal operating condition are sometimes irradiated with the beam.
When the extraction accuracy of a beam of a target ion species decreases, a sample becomes irradiated with a metal ion beam that should be essentially removed under normal circumstances and pollution occurred. Usually, an ion beam apparatus has a mass separator or the like in order to take out only a necessary nonmetallic ion beam from many kinds of ions including metallic ions generated by an ion generation source. When the applied voltage of an electrode of a mass separator (the current value of a coil when the coil is used for magnetic field generation) drops gradually due to discharge and the like, with the processing beam extracted, then in the process of a decrease in this voltage (or current) the sample is irradiated with beams other than an ion beam that should be essentially be used. Metal pollution occurs if a metallic ion beam is included in these unintended ion beams.
In order to ensure that neutron particles including metallic particles generated in an ion generation source do not reach the sample as they are, usually, the ion beam orbit from the ion generation source to the sample is bent and not straight. Therefore, a defector that deflects the traveling direction of ion beams toward the sample is used in an ion beam apparatus. In general, a deflector that deflects ion beams by an electric field is used.
Also in this case as described above, if the applied voltage of an electrode of a deflector drops gradually due to discharge and the like, with the ion beam extracted, then the ion beam deflects from the target orbit, with the result that metal pollution occurs if a metal portion becomes irradiated with the ion beam.
A sputtered metal material remaining within a processing optical system, which is generated by irradiation with an unintended ion beam like this, reaches the sample by the transport effect associated with the static electric force of the processing ion beam immediately after restoration of the apparatus following taking discharge-related measures, and this may sometimes cause pollution.
Such irregularities occur also when the power supply control system of an ion beam apparatus is stopped due to an electric power failure and the like. Also, metal pollution occurs similarly when the operator makes mistakes in setting beam conditions when changing the processing beam species and the beam irradiation conditions.
The object of the present invention is to provide a charged particle beam processing apparatus capable of improving yields by suppressing the spread of metal pollution to a semiconductor manufacturing process to a minimum extent.